CLJS-3324: hash-map behavior differs from Clojure (#102)

* CLJS-3324: hash-map behavior differs from Clojure

Add runtime check to hash-map w/o changing perf.

Add runtime check to PersistentHashMap.fromArrays w/o significant perf change.

hash-map is also an inlining macro which invokes PersistentHashMap.fromArrays.
naive use of partition leads to garbage in / out. Pad to fill in the missing value,
then remove - then when computing the values drop when we hit a non-pair. This way
we get non-matching array lengths and can defer to the runtime check.

Add tests.

Author: swannodette

src/main/cljs/cljs/core.cljs

@@ -8052,7 +8052,9 @@ reduces them without incurring seq initialization"
     (let [len (alength ks)]
       (loop [i 0 ^not-native out (transient (.-EMPTY PersistentHashMap))]
         (if (< i len)
-          (recur (inc i) (-assoc! out (aget ks i) (aget vs i)))
+          (if (<= (alength vs) i)
+            (throw (js/Error. (str "No value supplied for key: " (aget ks i))))
+            (recur (inc i) (-assoc! out (aget ks i) (aget vs i))))
           (persistent! out))))))
 
 (set! (.-createWithCheck PersistentHashMap)
@@ -8926,7 +8928,10 @@ reduces them without incurring seq initialization"
   [& keyvals]
   (loop [in (seq keyvals), out (transient (.-EMPTY PersistentHashMap))]
     (if in
-      (recur (nnext in) (assoc! out (first in) (second in)))
+      (let [in' (next in)]
+        (if (nil? in')
+          (throw (js/Error. (str "No value supplied for key: " (first in))))
+          (recur (next in') (assoc! out (first in) (first in')) )))
       (persistent! out))))
 
 (defn array-map

src/main/clojure/cljs/core.cljc

@@ -2623,9 +2623,12 @@
 (core/defmacro hash-map
   ([] `(.-EMPTY cljs.core/PersistentHashMap))
   ([& kvs]
-   (core/let [pairs (partition 2 kvs)
+   (core/let [pairs (map
+                      (core/fn [pair]
+                        (remove #{::missing} pair))
+                      (partition 2 2 (repeat ::missing) kvs))
               ks    (map first pairs)
-              vs    (map second pairs)]
+              vs    (map second (take-while #(= 2 (count %)) pairs))]
      (vary-meta
        `(.fromArrays cljs.core/PersistentHashMap (array ~@ks) (array ~@vs))
        assoc :tag 'cljs.core/PersistentHashMap))))

src/test/cljs/cljs/collections_test.cljs

@@ -1084,6 +1084,13 @@
   (testing "persistent vector invoke matches clojure"
     (is (thrown-with-msg? js/Error #"Key must be integer" ([1 2] nil)))))
 
+(deftest test-cljs-3324
+  (testing "hash-map behavior with missing values matches clojure"
+    (is (thrown-with-msg? js/Error #"No value supplied for key: :a"
+          (hash-map :a)))
+    (is (thrown-with-msg? js/Error #"No value supplied for key: :a"
+          (apply hash-map [:a])))))
+
 (comment
 
   (run-tests)